South Korea and the U.S. pledged to unite to meet the threat of North Korea developing weapons of mass destruction amid indications the country may be planning a third nuclear test.

The countries restated their commitment to coping with additional North Korean provocative actions and threats, such as the firing of a long-distance missile and a nuclear weapon test, South Korea’s National Defense Ministry said in an e-mailed statement today after a meeting earlier this week in Washington of the so-called Korea-U.S. Integrated Defense Dialogue.

It was the first round of talks between the defense authorities since North Korea launched a rocket April 13 that disintegrated shortly after takeoff. North Korea has escalated threats against South Korea and the U.S. in recent weeks as the new leader Kim Jong Un celebrates the centennial of the birth of the country’s founder, his late grandfather Kim Il Sung.

U.S. satellite pictures from April 18 may show further activity at North Korea’s Punggye-ri nuclear testing site, the U.S.-Korea Institute at Johns Hopkins School of Advanced International Studies in Washington said today on its website called “38 North.”

The imagery “supports the contention that preparations are continuing and that the North Koreans are preceding as if the test go-ahead decision has already been made,” the report said. The pictures don’t “give any indication of when that detonation may take place.”